This invention relates to a directional coupler for coupling together single-polarization or polarization-maintaining optical fibers, and more particularly, to such a directional coupler having an improved extinction ratio.
Single polarization fibers are useful in fiber optic rotation sensors, coherent communication systems, etc., because such fibers can transmit information on both phase and the state of polarization. Directional couplers, polarization controllers and polarizers have been developed for such fiber optic systems.
It is an object of the present invention to provide an improved directional coupler for coupling single-polarization optical fibers which is significantly improved in polarization maintenance or extinction ratio.